Ventilation and air cleaning systems are a vital part of the general design of any nuclear facility. The combination of a well designed ventilation system with thorough cleaning of exhaust air is the main method of preventing radioactive contamination of the air in working areas and in the surrounding atmosphere. This report provides the latest information on the design and operation of off-gas cleaning and ventilation systems for designers and regulatory authorities in the control and operation of such systems in nuclear establishments. Contents: 1. Scope; 2. General purposes of off-gas cleaning and ventilation systems; 3. Health and safety requirements for design of off-gas cleaning and ventilation systems in nuclear facilities; 4. System design; 5. Typical containment, ventilation systems and components; 6. Filter properties; 7. Filter testing methods; 8. Conclusions; Annex: Standards and Rules.